Apparatus for electrical uses



June 30, 1936. E. E. FRANZ 2,045,985

APPARATUS FOR ELECTRICAL USES Filed July 27, 1953 3 Sheets-Sheet 1 J3 INVENTOR E. E. FRANZ A TTORNEV June 30, 1936. E E FRANZ 2,045,985

I APPARATUS FOR ELECTRICAL USES Filed July 27, 1933 3 Sheets-Sheet 2 FIG. .9.

I I I I I I I 1 I I I I I I I I I I I I I I I I I I INVENTOR E. E. FRANZ .4 Tron/vs) June 30, 1936. E. E. FRANZ APPARATUS FOR ELECTRICAL USES Filed July 27. 1933 3 Sheets-Sheet S FIG I2 f'IG.

INVENTOR E. E. FRANZ ATTORNEY lkdisaticviewin Pull-heath! UNITED STATES PATENT OFFICE I ,Zifmm Us?! Wests-n Electric Company, Yon-LN. 1., a corporation of New York lium-to New m invention relates to apparatus for electrii'alwll esandmore particularlytocontinuwsly vlriableapparatusforuseasmheostat clannt, impedances. condensers o and the like. I

An objected the invention is to produce arfldsdthecharacterdescribedwhichmayhave a lane range at variability of a characteristic suchas.inductanoe.capacity.

ldheatMetamnd/orwhichmprybesubstan- JIIlyvariabIeovertheentirermge.

witn this and other obiects in view one embodlllmt'of the'invention con a core 'llvlnganaxhllineinhelicaLspiralorother '16 fun and which anon-terminating morsubstantially toroidal segments Joined towabuttingagainsteachotherandupon whieliacondnctorof'anydesiredlength may be primed thus enabling the construction of an I melementhavinganydesiredmaidmum vcapacity with respect to a given characteristic 7W property. A sliding contact member mounted in simple and eifective fashion to dflealong on the element and thus'permit between one fixed-end of the element and the sliding contact of any desired continuously adjustable amount of the conductor.

objects and characteristic features of appear from the following dedescription of an embodiment thereof parts in the several figures I. it ase ni- 1 tic broken view in spective and partlyinseca resistance coil embodying the invennasinneotion onthelineHoiPig.4

It. dis a plan view of another v is a central longitudinal section thereof; perspective dathird embodiment;

7-1-3 mlhasideviewthereofasmountedinan beingshownin filled V m in with the accompanying drawrig. loisaviewslmilartol'ig. 1 oiafourthembodiment' Fig. 11 is a sectional view on the plane indicated in Fig. Fig. 12isasectio'nontheline i2-l2 of mg. 11; 5

Fig. 13 is a semi-diagrammatic view of a fifth embodiment, and r Fig. 14 is an exploded view of a pair of core sectionsasusedinFig. 13.

In the embodiment herein disclosed there is illustrated in-Figs. 1 to 5 inclusive a helical resistance coil of continuously variable resistance and practically unlimited'maximum resistance constructed in accordance with the invention mounted on a supporting base of any convenient construction. A metal bar mounted on the base 20 and of uniform cross section, here shown as substantially rectangular in section but which may be of circular, oval or any other desired form in this respect, is formed into auniformly helical core support 2|. Upon this support is positioned in end abutting sequence a series of preformed twisted toroidal sleeves 22 of electrically insulating materialsuch as a premolded and baked ceramic paste, premolded bakelite, vulcanite, etc. to form with the support 2| a continuous core of potentially unlimited extent and occupy ng a relatively small volume of space in proportion to the extent of surface available to be wound with a conductor. Each of the sleeves 22 may be preformed as a complete unit axially perforated to fit the bar 2| and may then be slid into place over the bar since thecurvature of the latter in the case now under consideration is uniform in all directions. It seems to be pref-. erable in practice-however, to premold each such sleeve 22 in two interlocking matched halves as shown best in Fig. 3 which may be applied directly to the bar 2| at the point of their permanent location. These half sleeves may be cemented or otherwise attached directly to the bar when in place although in general this is not advisable on account of the difference between the thermal coeflicients of expansion of the two materials.

A winding 22 of wire of appropriate metal or alloy as for example nichrome is positioned on the compound core as above formed, the surface of which may be formed with aprei'ormed spirally encircling groove to retain the turns of the winding in place. The winding extends around and along the core from a convenient point at or near one end thereof any desired distance to a second convenient point on the core where the winding may terminate and its end be fastened in any convenient fashion. This winding It may beputinplaceinanyconvenientway. Ifthe insulating sleeves 22 of the core are preformed axially perforated and whole toroidal tubes, each such sleeve may be wound individually before being put-in place on the bar 2| with an independent section of the winding, the adjacent ends of juxtaposui sections of the winding being subsequently united by any approved means such as welding or soldering after each sleevehasbeenslidintoplacealongthebar. If the sleeves be formed of interlocking matched half sleeves. a length of wire for a section of the winding might be WOlllld into a coreless helix a trifle larger thanthe core, then slid down over the completed core into position thereon, welded terminally to the preceding section of wire and drawn tautly into place on the core. 'In some cases the wire ilmightbe wound directly on the completed core.

When the winding 23 is finally in place, one end of the winding is connected to a convenient binding post 24 or other terminal of any approved type, and if it be intended to use the coil as a fixed value resistance, the other end of the winding may also be connected to a second terminal. If desired the coil may further be tapped at points intermediate its ends and leads brought out to other terminals to enable the use of any desired fixed fractional part of the winding.

A fixed value resistance coil thus constructed is simultaneously strikingly compact and well ventilated. A great length of winding is disposed within a relatively small volume of space; the winding is securely supported over its entire length; and all points of the winding are freely exposed to aiford efilcient removal of heat by atmospheric convection as well as by direct radiation. The coil can therefore, be used without damage under unusually heavy loads If the coil is to be used as a continuously variable resistance, the intermediate taps to terminals may be omitted and a sliding contact member provided to run along the coil. As disclosed and to this end a square metal shaft 28 is located in the axis of the helical core and rotatably mounted in the frame 20. A centrally correspondingly perforated metalblock ill slides snugly but easily on the shaft and is held in electrical contact with the shaft by a spring member II located in a corresponding groove in the block and pressing against the shaft. A duplex, resilient contact member 32 is rigidly attached to one side of the block 30 and is formed with a pair of integral complementary resilient guide and contact arms 33 which press against the wound core at opposite sides thereof and so make contact with the winding 23. 7 Thus the winding at its contact with the arms 33 is electrically connected through the arms 33, the block 30 and the shaft 28 with a terminal 34 connected to the shaft in any convenient manner. The shaft 28 is further provided with a knob or handle 35 and, if desired, an indicating device may also be associated therewith. This device may comprise a spirally slotted dial plate 36 appropriately marked with a'scale and an indicator 31 mounted to slide freely in the slot of the dial and also in a fixed radial guide 38 mounted under the dial on the base 20.

When the shaft is caused to rotate the block 30 rotates with the shaft -thereby causing the arms .33 to slide along the helix rotationally. Due to the screw form of the helix this will in turn cause the block 30 to slide correspondingly on the shaft 28. Thus all points of the 0011 may be traversed continuously by the contact arms 33 andhencetheportionofthecoilelectrically interposedbetweentheterminalsfland 3415 continuously variable at'will.

Forsomepurposes itmaybedesirabletohave the core substantiallycompletely composed of dielectric material only. Such a modified embodiment of the invention is disclosed in Figs. l3 and l4.'Inthiscase,if thecore4lbeheiical,ltis composed of identical, twisted, semi-circular, toroidal segments 4| which may interlock at abuttingends by meansof a square .mortice 42 and tenon 43 as indicated in Fig. 14. 1111s embodiment alsoillustrates a construction in which the interior of the helical coil is left entirely free of access for convecting air. The coil itself as a whole is rotatably mounted on end supports 44 Journalled in a frame 45 and the sliding contact member 48 is carried on a fixed bar 41 out-side of and parallel to the helix.

Again it may be desirable to limit the dimensions of the apparatus in one direction while ex tending it in both directions at right angles thereto. In this case as in the modified form 11- lustrated in Figs. 6 and 7, the core 5| instead of being coiled on a helical axis may be confined substantially to one plane and coiled with its cal in form since the curvature per unit length of the spiral decreases from the inner end of the spiral outwardly. Alsothe mechanism to carry the sliding contact must be modified since the radial distance of the block from the center around which it revolves is also variable when the contact moves along the spiral. Hence, as shown, in this instance the contact block 52 may be carried by and slide along 'a radial conducting arm 53 pivoted at the center of the spiral.

' A form is illustrated in Figs. 8V and 9 in which provision is made for maximum freedom of access for convecting air to all parts of the coil with minimum mutual interference of convection currents. In this instance the axis of the core 60 takes the form of a three dimensional conchoid, the path of a point revolving in a conical surface and movingaway from its apex. Here the sliding contact ll is carried by and slides on a rod 62 pivoted and movable to describe the surface of a cone parallel-to the general form of the coil. As in the case of the flat spiral last described, the core may be with or without a metal backbone and the core segments, while generally mutually similar are not mutually identical being of va ying principal curvature. As indicated in Fig. 9, the conchoidal element Bl may be mounted within a cage or skeleton support 63 having a disk 64 rotatably mounted in one end thereof to act as a supporting guide for the handle end of the contact slide rod 82.

It may be noted that in each case a characteristic feature of the structure is that the segments of the core form a non-self-terminating sequence of substantially toroidal sections. In the case of the helix the core does not return upon itself or close because each of the segments of the core is of double curvature although the curvature in both directions is constant In the fiat spiral it is because although the segments are only singly curved. their curvature diminishes outwardly from the center of the spiral; while in the conwhichaieeitheralikeorsimilarinshape. 'Ihus choid the segments are not only doubly but their curvature diminishes in both directions outwardly from the apex of the cone enveloping the conchoid.

In the case otthe flat form of Figs. 8 and 7, or of the conchoidal form of Figs. 8 and 9, ifthe core follow a logarithmic spiral, equal angular turnsoftheradialarmwillaltertheresistance value between the terminals by proportionately equal increments; whereas in the helical form of Fig. 1. equal angular turns of the knob represent equal additive increments of resistance. The form of the core may thus be easily shaped to cause the relation between angular turn of the actuating member and resultant change in resistance to assume any one of a variety of mathematical functional forms. a matter of considerable value in making a" resistance with an arbitrarily graduated scale for inclusion in a Wheatstone bridge, Kelvin bridge, etc., as part of any one of an infinite variety of testing devices.

Although thus far principally disclosed as embodied in a resistance coil, the invention is not confined to such. Figs. i0, i1 and 12 disclose a variable condenser made in accordance with the invention. A curvilinear core is formed and composed similarly to the cores previously described of segments ll of insulating material threaded on a supporting metal or non-metallic and insulating inner support ll carried on a base member 12. Condenser elements II are positioned between the segments II and have alternate interior and exterior terminals It and II respectively. .The condenser elements It may comprise single conductive plates between the segments 10, or as herein disclosed may each consist of .a group of interleaved conductive and insulating lamina. The exterior terminals I! are permanently connected together by a conductor I. connected to a terminal II. A tubular metal shaft II is slidabl'y mounted in the base I! to be reciprocable within the helical core and isso proportioned as to make wiping contact with eachoftheterminals'llinsuccessionasthe shaft advances along the axis of the helix. A terminal I. is electrically connected to the shaft.

It will be evident that acommon feature of the several embodiments described is the fact that the core is not self limiting or self terminating since it has in general the form of a non-remtrant or open coiled curve as distinguished from cores having the general form of a circle; oval. square, oblong or the like. A second commoncharacteristicisthateachcoreisbuiltup of a coiled sequence of axially curved segments arcuate it is possible to build up in relatively small space an apparatus of the kind referred to of practically unlimited capacity and with all of its parts conveniently and freely accessible.

It will be further evident that the embodiments hereindisclosed are illustrative merely and maybe widely modified and departed from without departing from the spirit and scope of the invention as pointed out in and limited solely by the appended claims.

What is claimed is:

1. In an electrical apparatus, a curved nonself-limiting core comprising component arcuate segments of continuously varying curvature Joined together end to end in a sequence whose axis has the general form of a curve selected from the clam of curves consisting ofthree dimensional concholds and flat spirals.

2.'In an electrical apparatus, a curved nonself-limiting core comprising component axially arcuate segments of continuously varying double curvature Joined together end to end in a sequence whose axis has the general form or a three dimensional conchoid.

3. In an electrical apparatus, a curved nonself-limiting core comprising component axially arcuate segments of continuously varying curvature joined together end to end in a sequence whose axis has the general form of a curve selected from the class oicurves consisting of three dimensional conchoids and fiat spirals, a conductive member carried by the core, and a contact member slidable along the conductive member.

4. In an electrical apparatus. acurved nonself-limiting core comprising component axially segments of continuously varying double curvature Joined together end to end in a sequence whose axis hasythe general form of a three dimensional conchoid, a conductive member carried by the core. and a contact member slidable along the conductive member.

. 5. In an electrical apparatus, a core comprising component axially arcuate segments of continuously and uniformly varying double curvature joined together end to end.

6. m an electrical apparatus, a core comprising component axially arcuate segments of continuously and uniformly varying single curvature Joined together end to end.

7. In an electrical apparatus, a core comprising component axially arcuate segments of continuously and uniformly varying curvature joined together end to end.

. IRWIN E. FRANZ. 

